<template>
    <div class="list">
        <li class="item"
            v-for="item in letters"
            :key="item"
            @touchstart="handleTouchStart"
            @touchmove="handleTouchMove"
            @touchend="handleTouchEnd"
            @click="handleLetterClick"
            :ref="item"
        >
            {{item}}
        </li>
    </div>
</template>

<script>
    export default {
        name: "CityAlphabet",
        props: {
            cities: Object
        },
        computed: {
            letters() {
                const lettersArr = []
                for (let i in this.cities) {
                    lettersArr.push(i)
                }
                return lettersArr;
            }
        },
        data() {
            return {
                touchStatus: false,
                startY: 0,
                timer: null
            }
        },
        updated() {
            this.startY = this.$refs['A'][0].offsetTop;
        },
        methods: {
            handleLetterClick(e) {
                // console.log(e.target.innerText)
                this.$emit("change", e.target.innerText)
            },
            handleTouchStart() {
                this.touchStatus = true
            },
            handleTouchMove(e) {
                if (this.touchStatus) {
                    if (this.timer) {
                        clearTimeout(this.timer)
                    }
                    this.timer = setTimeout(() => {
                        const touchY = e.touches[0].clientY - 79;
                        const index = Math.floor((touchY - this.startY) / 20);
                        if (index >= 0 && index < this.letters.length) {
                            this.$emit('change', this.letters[index]);
                        }
                    }, 8)

                }
            },
            handleTouchEnd() {
                this.touchStatus = false
            }
        }
    }
</script>

<style lang="scss" scoped>

    @import "~@/styles/varibles.scss";

    .list {
        display: flex;
        flex-direction: column;
        justify-content: center;
        position: absolute;
        top: 1.58rem;
        right: 0;
        bottom: 0;
        width: .4rem;

        .item {
            text-align: center;
            line-height: .4rem;
            color: $bgColor;
        }
    }
</style>
